1. Field of the Invention
The present invention relates to a high-temperature nuclear reactor having spherical fuel elements which are arranged approximately ring-shaped about a graphite core, and in particular, relates to a nuclear pebble bed reactor providing for inherent passive stabilization in the event of damage.
2. Discussion of the Prior Art
High-temperature nuclear reactors with spheroid fuel elements are presently known. Different concepts have been developed with regard to the safety regulations in the event of encountered damage. For high-temperature nuclear reactors having a lower capacity there can be achieved an "inherent stabilization" in the event of encountered damage, which signifies that upon the failure of all active cooling systems and pressure release, there can be maintained a temperature of 1600.degree. C. (which may not be exceeded in order to prevent release of the fission product) through natural heat removal. This requires a prerequisite capacity restriction for the single core to about 250 MW.sub.th.
Consequently, there has been already been described a modified core type which incorporates an axial graphite column about which there are arranged spherical fuel elements in an approximately annular or ring-shaped configuration (refer to K. Peterson et al. "Efficiency of Inherent Protection Mechanisms for an Improved HTR Safety Concept", in a paper presented at the Specialists Meeting on Gas-cooled Reactor Safety and Licensing Aspects, Lausanne, Sept. 1-3, 1980). Such a high-temperature reactor with a ring-shaped core can be designed for a capacity of 350 MW.sub.th and higher; however, its construction is more complicated and the selection of the diameter of the center column must be met with great care, wherein there must also be considered that over lengthy periods of time there can be encountered problems of strength resulting from the continual influence of high neutron flux.